Dual band ridged feed horn



April 23, 1968 J. o. OSBORN DUAL BAND RIDGED FEED HORN 5 Sheets-Sheet 1 Filed July 20, 1965 INVENTOR. Jimmie Dean Osborn ATT'YS.

A ril 23, 1968 J. D. OSBORN DUAL BAND RIDGED FEED HORN S Sheets-Sheet Filed July 20, 1965 INVENTOR. Jimmie Dean Osborn ATTYS April 23, 1968 J. o. OSBORN DUAL BAND RIDGED FEED HORN 5 Sheets-Sheet 5 Filed July 20, 1965 I N VEN TOR. Jimmie Dean Osborn ATTYs.

United States Patent DUAL BAND RIDGED FEED HGRN This invention pertains generally to a multiple fre quency antenna feed assembly and more particularly to such a feed assembly for use with a reflector antenna.

In applications such as monopulse radar tracking, it is desirable to radiate independent signals on different microwave frequencies using the same antenna structure for the different frequencies. With microwaves it is generally desirable to provide an antenna system which has a highly directional beam pattern and which is adapted to obtain the maximum advantage according to the particular service for which the antenna is intended. Where the antenna is in the form of a feed horn and a curved reflecting surface, it is difficult to get multiple frequency operation of the antenna without degradation of the reflector performance.

In the past, multiple frequency operation using a feed horn and reflector antenna has been accomplished, for instance, by using an array of feed horns or by using a single dual frequency feed horn with the two signals having orthogonal polarization. The propagation characteristics of the two polarizations are different in the latter structure thereby severely limiting the usefulness of the antenna.

It is one object of this invention to provide an improved multiple frequency antenna feed assembly which is relatively simple and inexpensive to produce.

It is another object of this invention to provide an improved antenna horn and feed assembly for use with a reflector, wherein a plurality of frequencies are radiated by a single horn, thereby allowing the feed assembly to perform simultaneous monopulse tracking, communications and data transmission.

One feature of this invention is a multiple frequency antenna feed assembly including a ridged waveguide having a wide bandwidth capability structure coupled to a ridged horn with the ridged waveguide terminating in a hybrid junction, and a second waveguide connected to the ridged waveguide structure to couple electromagnetic energy therebetween. This connection may be made through coaxial line sections which have a probe at one end extending into the standard waveguide and a probe at the other end extending into the ridged Waveguide Structure.

Another feature of this invention is a horn feed assembly for a reflector antenna having a wall partitioning the ridged waveguide into first and second waveguide channels, a tapered ridge in each of said channels, and an impedance match between the ridged waveguide and the hybrid junction for coupling electromagnetic energy of one polarization and in one frequency band within the wide bandwith capability of the ridged waveguide between the hybrid junction and the ridged waveguide. The center conductors of coaxial line sections serve as probes, and are equally spaced and have one end extending into the concentrated electric field of the H plane of a second Waveguide and each of the other ends extending into the concentrated electric field of the H plane in one of the channels in the ridged waveguide for coupling the electromagnetic energy of the same polarization and in another frequency band within the wide bandwidth capability of the ridged waveguide between the standard and ridged Waveguide.

Still another feature of this invention is a horn feed assembly for a reflector antenna having two horns connected to two ridged waveguides which terminate in a 3,380,057 Patented Apr. 23, 1968 hybrid junction and transitions between the ridged waveguides and the hybrid junction for coupling electromagnetic energy of one polarization and in one frequency band therebetween. A second waveguide is coupled to an H plane junction which has two arms connected to the respective ridged waveguides for coupling electromagnetic energy of the same polarization and in another frequency band between the second waveguide and the ridged waveguides.

In the drawings:

FIG. 1 is a perspective view showing the multiple frequency antenna of this invention;

FIG. 2 is a perspective view of one embodiment of the device of this invention;

FIG. 3 is a cross-sectional view taken along the lines 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along the lines 44 of FIG. 3;

FIG. 5 is a cross-sectional view taken along the lines 5-5 of FIG. 3; and

FIG. 6 is a perspective view of a second embodiment of the invention.

The device of this invention can be used as a feed for a reflector antenna such as used in a two lobe monopulse radar tracking system. It consists of a single ridged horn coupled to one end of a ridged waveguide which has a wide bandwidth capability. A wall partitions the ridge waveguide structure into two waveguide channels with a tapered ridge in each channel. The other end of the ridged waveguide terminates in a hybrid junction. Impedance matching means serves to couple electromagnetic energy of one polarization and in one frequency band within the wide bandwidth capability of the ridged waveguide between the ridged waveguide and the hybrid junction. A second waveguide is attached to the ridged waveguide by a pair of coaxial line sections having their center conductors extended to serve as probes. The sections are equally spaced and have the probes of one end extending an equal distance into the concentrated electrical field of the H plane in the second waveguide, and probes on the other end each extending into the concentrated electrical field of the H plane in one of the channels in the ridged waveguide. The coaxial sections serve to couple the electromagnetic energy of the same polarization and in another frequency band within the wide bandwidth ca pability of the ridged waveguide between the standard waveguide and the ridged waveguide.

In another embodiment, two horns are provided. Each of the horns is coupled to a ridged waveguide, and the ridged waveguides terminate in a hybrid junction. The standard waveguide is coupled directly to the ridged Waveguide of each horn through an H plane junction, with standard bandpass filters providing isolation between channels.

Referring more specifically to the figures of the drawings, FIG. 1 shows the feed horn 10 mounted to a parabolic reflector 14 used, for instance, in a two lobe monopulse radar tracking system. Mounted to the antenna 14 is reflector 16 for focusing the microwaves at the mouth 18 of the horn 20.

A better understanding of the construction of the feed horn 10 can be had by referring to FIGS. 2 through 5. The horn 20 has tapered ridges 22 that start at the neck of the horn and extend with an increased taper until they terminate at 25 just short of the mouth 18 of the horn. Additional ridges 28 extend from the mouth 18 of the horn midway between ridges 22 to point 29 in the horn.

Coupled to the horn 20 is a ridged waveguide structure 30. A wall 32 extends the length of the waveguide structure 30 and partitions the same into two separate wave guide channels 35 and 36. Tapered ridges 38 and 39 extend the length of the channels 35 and 36 respectively, and matingly engage ridges 22 in horn 20, and terminate at the end 46 of the waveguide 30. Surrounding the end 41 is an integral fiange portion 42.

A hybrid junction has a flange 52 integral with one end thereof which is coupled to the flange 42 of wave guide by screws 54. The tapered partition 55 extends from the aperture 57 leading from the E plane arm 58 of the junction 5%. The partition 55 mates with the wall 32 to partition the H plane arm of the junction on either side of the partition into channels 60 and 61 that are matched to the channels 35 and 36 respectively. The side walls 64 of junction 50 are formed in a stepped discontinuity for wave shaping purposes until they meet with the integral flange portions 65 and 66 which delimit the aperture 68 in the junction 50. The E plane arm 58 has an aperture 70 delimited by integral flange portions 74 and 75. The fiange portions 66 and 75 are used to mount the feed horn assembly 10 to microwave transmitting and receiving equipment.

A second waveguide 89 has integral flanges 82 and 83 delimiting an aperture 85. A connecting piece 87 made of electrical conducting material has similar holes 90 and 91 equidistantly spaced therein and passing therethrough. Center conductors 94 and 95 pass through the holes 90 and 91 and cooperate therewith to form coaxial line sections. The center conductors are extended into the waveguide 81) to act as probes 97 therein, and they each extend into one of the channels 35 and 36 to act as probes 98 therein. The connecting piece 87 is mounted to the integral bracket 100 of the second waveguide 80 and the integral bracket 101 of the ridged waveguide 31) by the screws 1&4 and 105 respectively.

For illuminating the target the horn 20 is excited by a transmitter (not shown) coupled to the radiating antenna 14 through the aperture 68, the hybrid junction 51) and the ridge waveguide structure 30. The hybrid structure 50 channels equal amounts of wave energy to each waveguide channels 35 and 36 of the ridged waveguide 36, which is designed to operate over a wide bandwidth of frequencies as for example from 4 gc. to 17 gc. The tracking beam could lie, for instance in the Ku band (12.4 gc. to 18 gc.) and in a typical installation the communication channel could also be within the Ku band so that no separate input would be required for communication. During transmission of the tracking and communications beams, data could be transmitted in the X band (5.2 gc. to 10.9 gc.) through the second waveguide 80 and coupled by the coaxial sections to the channels 35 and 36 of the ridged waveguide 30 and transmitted from the horn 20.

The stepped discontinuity 64 in the hybrid junction 56 and the dimensions of the ridged waveguide 30 are such as to propagate the electromagnetic energy in the Ku band frequency in the TE and TE modes and to attenuate all higher order modes. However, if the ridges 28 and 2? are removed, the Ku band TEgo mode is excited. This is desirable in some instances because it can be used for Ku band beam width control. The tapered ridges 3S and 39 in the channels 35 and 36 serve as a transition (impedance match) when coupling the electromagnetic energy between the hybrid junction 51) and the ridged waveguide structure 30. The ridges 22 and 28 in the horn 20 provide a gradual transformation of impedance from the characteristic wave impedance of the horn to the intrinsic impedance of free space.

The probes 97 extend into the area of concentrated H plane waves in the waveguide 81 The distance of the end of the probes from the wall 108 of the waveguide determines the nature of the impedance match between the probe and the waveguide. The probes 98 that extend into the channels 35 and 36 are located in a close proximity to the ridges 38 and 39, respectively, where the hi hest concentration of H plane waves are located. The coaxial sections 94 and $5 are equidistantly spaced so that each couples a balanced amount of electromagnetic energy in the X band between the second waveguide $0 and the ridged waveguide structure 30. Because of the dimensions of the ridged Waveguide structure 30, as heretofore described, it operates over a frequency range of 8 gc. to 17 gc. The X band waves are propagated therethrough in the dominant or TE mode.

During the receiving cycle, the signal from the target excites the feed horn 10 to provide information of the target location. The signals developed by the horn 20 on reception are vectorially added and vectorially subtracted by the hybrid structure in the well known manner to develop the conventional sum signal at aperture 68 and the difference signal at aperture 70. The signals are applied therefrom to the receivers of the tracking and communication system. The coaxial line sections are impedance matched to couple the received X and data information from the ridged waveguide structure 36 to the second waveguide 89 where it is applied to a data receiver. Using this method of coupling the electromagnetic energy in the X hand between the two waveguides, eliminates the need for fibers to provide isolation between the channels. Some applications of the horn 19, however, would require a filter in the X band circuitry which would pass the X band but reject the Ku band.

A second embodiment of the invention is shown in FIG. 6. Many of the elements of this embodiment are the same as described heretofore so the same numbers will be used to identify similar elements.

The operation of this embodiment is substantially the same as heretofore described with exception that two horn assemblies are used. The ridged horns 110 and 111 are connected respectively to one end of ridged waveguides 114 and 115. The ridged waveguides 114 and 115 serve the same function as the waveguide channels 35 and 36 in the ridged waveguide structure 30, and they are terminated in the hybrid junction 50 which provides the sum feed 68 and the difference feed 58. The X band data feed 85 is connected to a second waveguide 80 as previously described. However, rather than using coaxial sections to couple the electromagnetic energy in the X hand between the second waveguide 80 and the ridged waveguide, the electromagnetic energy in its dominant or TE mode is coupled from an H plane junction 119, coupled to the standard waveguide 80, to each of the ridged waveguides 115 and 114 by the arms of waveguide sections 121 and 122. Standard bandpass filters in the waveguide coupling sections 121 and 122 pass the X band but reject the KM band. No filters, however, are required in the Ku band circuitry to reject the X band.

Although these particular embodiments of the invention have been described using a feed horn with only dual frequency band capability, it should be clear that additional channels could be added by varying the dimensions of the waveguides and using suitable filters all of which would fall within the design area.

What has been described, therefore, is a relatively simple and inexpensive multiple frequency antenna feed assembly that may use only one horn.

I claim:

1. A multiple frequency antenna and feed assembly including in combination, ridged horn means, first ridged waveguide means coupled to said ridged horn means, a hybrid junction coupled to said first ridged waveguide means, said ridged waveguide means having transition means for coupling electromagnetic energy of one polarization and in one frequency hand between said ridged waveguide means and said hybrid junction, a second waveguide, coupling means for coupling the electromagnetic energy of said one polarization and in another frequency band between said first ridged waveguide means and said second waveguide.

2. A multiple frequency antenna and feed assembly including in combination, ridged horn means, first ridged waveguide means coupled to said ridged horn means and having a bandwidth including first and second spaced frequency bands, :1 hybrid junction coupled to said first ridged waveguide means, said ridged waveguide means having transition means for propagating electromagnetic energy in said first frequency band between said ridged waveguide means and said hybrid junction, a second waveguide, coupling means for coupling electromagnetic energy in said second frequency band between said first ridged waveguide means and said second waveguide.

3. A multiple frequency antenna and feed assembly including in combination, ridged horn means, first ridged waveguide means having first and second waveguide channels coupled to said ridged horn means and having a bandwidth including first and second spaced frequency bands, a hybrid junction coupled to said first ridged waveguide means, said ridged waveguide means having impedance matching means for propagating electromagnetic energy in said first frequency band between said ridged waveguide means and said hybrid junction, a second Waveguide, coupling means for coupling electromagnetic energy in the TE mode and in said second frequency hand between said first and second channels of said first ridged waveguide means and said second waveguide.

4. A horn feed assembly and a reflector forming an antenna and including in combination, a ridged horn, a first waveguide having first and second ends with said first end coupled to said horn, said first waveguide having a bandwidth including first and second spaced frequency bands, a wall partitioning said first waveguide into first and second channels and a tapered ridge in each of said channels, a hybrid junction coupled to said first waveguide at said second end thereof, impedance matching means including said tapered ridges for coupling electromagnetic energy of one polarization and in said first frequency band between said first waveguide and said hybrid junction, a second waveguide, means including a pair of coaxial line sections each having a probe at one extending into said second waveguide and a probe at the other end extending into one of said first and second channels for coupling the electromagnetic energy of said one polarization and in said second frequency band between said first waveguide and said second waveguide.

5. A horn feed assembly and a reflector forming an antenna and including in combination, a rigid horn, a first waveguide structure having first and second ends with said first end coupled to said horn, a wall partitioning said first waveguide structure into first and second waveguide channels and a tapered ridge in each of said channels, a hybrid junction coupled to said first waveguide structure at said second end thereof, impedance matching means including said tapered ridges for propagating waves in one frequency band between said first waveguide structure and said hybrid junction, a second waveguide, connecting means for connecting said second waveguide to said first waveguide structure, two cylindrical holes equidistantly spaced and extending through 6 said connecting means, center conductors extending through said holes, said holes and said center conductors forming coaxial line sections, said center conductors in said coaxial line. sections forming probes at one end thereof and extending equal distances into the concentrated electric field of the H plane in said second waveguide, and said center conductors forming probes at the other end thereof and each extending into the concentrated electric field of the H plane in one of said first and second channels for coupling the electromagnetic energy in the TE mode and in another frequency band between said first waveguide structure and said second waveguide.

6. A multiple frequency antenna and feed assembly including in combination, first and second ridged horns, first and second ridged waveguides having first and second ends with said first ends coupled to said first and second ridged horns respectively, said first and second ridged waveguides having a bandwidth including first and second spaced frequency bands, a hybrid junction coupled to said first and second ridged waveguides at said second ends thereof, impedance matching means including said ridges for coupling electromagnetic energy of one polarization and in said first frequency band between said first and second ridged waveguides and said hybrid junction, a second waveguide, and coupling means for coupling the electromagnetic energy of said one polarization and in said second frequency band between said second waveguide and said first and second ridged waveguides.

7. A horn feed assembly and a reflector forming an antenna and including in combination, first and second ridged horns, first and second ridged waveguides having first and second ends with said first ends coupled to said first and second ridged horns respectively, said first and second ridged waveguides having a bandwidth including first and second spaced frequency bands, a hybrid junction coupled to said first and second ridged waveguides at said second ends thereof, impedance matching means including said ridges for propagating electromagnetic energy in the TE mode and in said first frequency band between said first and second ridged waveguides and said hybrid junction, a second waveguide, an H plane junction having said second waveguide coupled thereto, said H plane junction having first and second waveguide sections coupled to said first and second ridged waveguides for coupling the electromagnetic energy in the TE mode and in said second frequency band between said first and second ridged waveguides and said second waveguides.

References Cited UNITED STATES PATENTS ELI LIEBERMAN, Primary Examiner. 

1. A MULTIPLE FREQUENCY ANTENNA AND FEED ASSEMBLY INCLUDING IN COMBINATION, RIDGED HORN MEANS, FIRST RIDGED WAVEGUIDE MEANS COUPLED TO SAID RIDGED HORN MEANS, A HYBRID JUNCTION COUPLED TO SAID FIRST RIDGED WAVEGUIDE MEANS, SAID RIDGED WAVEGUIDE MEANS HAVING TRANSITION MEANS FOR COUPLING ELECTROMAGNETIC ENERGY OF ONE POLARIZATION AND IN ONE FREQUENCY BAND BETWEEN SAID RIDGED WAVEGUIDE MEANS AND SAID HYBRID JUNCTION, A SECOND WAVEGUIDE, COUPLING MEANS FOR COUPLING THE ELECTROMAGNETIC ENERGY OF SAID ONE POLARIZATION AND IN ANOTHER FREQUENCY BAND BETWEEN SAID FIRST RIDGED WAVEGUIDE MEANS AND SAID SECOND WAVEGUIDE. 